A continuous uncoiler for coils of web lengths of material, such as paper, can provide a continuous supply of the web to processing equipment including a continuous cross-cutter cutting the web into a succession of sheets.
Characteristically such an uncoiler provides means for rotatively mounting one coil so its web length can be continuously pulled forwardly so as to form a continuously feeding span, together with means for rotatively mounting a second coil axially parallel to the first coil and so as to be overlapped by the span feeding from the first coil. For continuous action, when the first coil approaches exhaustion, the last portion of its web is connected to the front end of the second coil's web length so that without interruption the second coil continues with the web feeding.
It follows that the interconnection between the exhausting and new coil webs must be effected while they continuously travel forwardly. An apparently simple way to do this is to first apply a transverse strip of pressure-sensitive adhesive to the outside of the front end of the web of the second coil so that by pressing the overlapping traveling web from the first or exhausting coil against the second coil's periphery, rotation of the second roll effects the connection adhesively. The coils can be mounted by spindles rotatively powered to control web tension to the value required for span tautness without web breakage and to rotate the second coil to bring the strip of adhesive into position for contact by the overlapping web. The second coil is normally brought to a peripheral velocity equalling the linear velocity of the continuously pulled web.
The interconnection between the webs must be made before the trailing end of the web from the first or exhausting coil leaves that coil's spindle because there must be some web backtensioning to maintain the span of web overlapping the second or new roll. Consequently, there is a residual portion of the overlapping web left trailing behind the interconnection made by the adhesive. This forms a tail that should be cut off neatly and as close as possible to the adhesive interconnection, to avoid trouble at the processing equipment.
The cut-off can be made by a flying knife which while cutting travels momentarily with the traveling webs. For precision control of the knife, computors have been used intended to take into consideration the web velocity, the position of the adhesive interconnection and the response time of the flying knife. The initial and servicing costs of such precision control are high and they are not always affordable. It is not uncommon to actually stop what should be a continuous unwinder so that the tail of web can be manually cut neatly and close to the adhesive interconnection. This requires stoppage of the processing equipment which should be fed continuously by the web lengths.